ZK-AS21 220W2+350W Bluetooth Power Amplifier Board - Flexible 18-36V

Our review of the ZK-AS21 finds it is a practical, power-focused amplifier board for hobbyists and installers who need flexible inputs and strong bass support. The bottom line: this module pairs two TPA3255 chips for substantial output and offers Bluetooth 5.1 plus AUX and USB flash playback, making it a compact solution for DIY speaker builds, vehicle installs, or adding amplification to a home subwoofer. It is best for users who can provide a stable DC supply above 18V and who want treble and bass controls to tailor sound.

Key Features

• TPA3255 HIFI CHIP: Dual TPA3255 chips deliver high-efficiency amplification so the board can handle demanding music passages with lower heat compared with older class AB designs.
• Wide voltage input: Support for 18-36V input gives flexibility for vehicle batteries or common DC adapters, allowing use across several installations.
• Multi-input options: Bluetooth 5.1, AUX and USB flash drive playback (FAT32) let you source audio from phones, wired sources or stored files without extra converters.
• TREBLE & BASS CONTROL: Dedicated high and low frequency knobs provide tone shaping so you can dial in clearer highs or stronger, layered bass for a subwoofer.
• Protection functions: Built-in short circuit, undervoltage, overvoltage and clipping protection help protect speakers and the board during setup or demanding use.
• Customizable Bluetooth: Bluetooth name and password can be set through the companion mobile app, reducing accidental pairings in shared environments.

Who It's For

The ZK-AS21 suits DIY audio builders, car audio enthusiasts and small home theater tinkerers who want a compact amplifier module with modern Bluetooth and tone controls. It is a strong pick when you need a flexible 18-36V supply range and want the ability to power a pair of satellite speakers plus a subwoofer using the module's outputs.

Those who should look elsewhere include buyers who cannot provide a DC source above 18V or who need an out-of-the-box enclosed amplifier with consumer controls and finished chassis; this board is a module intended for installation into a custom enclosure or vehicle wiring harness.

Pros & Cons

Pros

• High output capability from dual TPA3255 chips gives robust sound and headroom for subwoofer use.
• Multiple inputs including Bluetooth 5.1 and USB flash playback make it versatile without extra gear.
• Tone controls for treble and bass allow quick tonal adjustments for different speaker setups.
• Protection features provide reassurance during installation and operation.

Cons

• Requires a DC supply above 18V, so it is not suitable for users who only have low-voltage adapters.
• As a board-level module it needs careful mounting and wiring; beginners may prefer a finished chassis product.

Specifications

Amplifier chips	Dual TPA3255
Power output	Up to 220W x2 + 350W (peak music)
Input voltage	18V - 36V DC
Bluetooth	Bluetooth 5.1 with app-configurable name and password
Inputs	Bluetooth, AUX, USB flash (FAT32)
Protections	Short circuit, undervoltage, overvoltage, clipping

Our Verdict

The ZK-AS21 is a solid-value amplifier board for anyone building custom speakers or upgrading a vehicle audio system who can supply an 18V or higher DC source. With dual TPA3255 chips, tone controls and modern Bluetooth features it delivers flexible connectivity and strong bass potential, though it requires careful installation since it is a board-level component.

Frequently Asked Questions

What minimum voltage is required?
The board requires a DC supply higher than 18V to operate reliably.

Can I play audio from a USB stick?
Yes, the board supports USB flash drive playback formatted as FAT32.

Does it include protection features?
Yes, it includes short circuit, undervoltage, overvoltage and clipping protection to safeguard the board and connected speakers.